I-24 passes through the lower Pennsylvanian rocks of the Pounds Escarpment, roughly 10 to 20 mi ( 15 to30 km) south of Marion, Illinois (Fig. 1). This escarpment is a cuesta formed of resistant basal Pennsylvanian sandstones. Roadcuts along the interstate have made accessible nearly all of the Caseyville Formation and the basal portion of the Abbot Formation. The roadcuts are approximately 20.5 mi (33 km) south of the interchange of Illinois 13 with I-57 at Marion, Illinois (Fig. 1), and 2.7 miles(4.3 km) north of the Vienna interchange of U.S. 45 with I-24.

Figure 2 shows the exact location of the I-24 roadcuts on aportion of the Vienna 7½-minute Quadrangle.The upper roadcut is in the E½NE¼Sec.8, T.12S., R.3E., Johnson County, Illinois.The lower cut is found in the E½NE¼Sec. 17, and the NW¼ Sec.16, T.12S., R.3E., Johnson County, Illinois.

The Pennsylvanian rocks are well exposed in lower and upper sets of cuts on both sides of the interstate. The shoulders are wide and paved, and provide room for a group of vehicles to pull completely off the road. However, it is still advisable for any large group planning a formal field trip to first check with the state police.

Separate cuts have been made for the northbound and southbound lanes on I-24; thus, four walls of rock are present and separate stops can be made (Fig. 2).